The asynchronous hormonal induction of lactose synthetase components, alpha-lactalbumin and galactosyltransferase, in relation to lactose secretion by mouse mammary explants.
Hormonal induction of the lactose synthetase components, alpha-lactalbumin and galactosyltransferase, in relation to the induced levels of lactose synthetase activity and lactose secretion by mammary gland explants from mature virgin mice was examined. During 6 days of culture in the presence of insulin, cortisol, prolactin and triiodothyronine mammary explants accumulated progressively increasing amounts of alpha-lactalbumin. By contrast, galactosyltransferase and lactose synthetase activities were maximal on day 3, and then declined; the time course of lactose secretion was similar to that of galactosyltransferase and lactose synthetase activities. Cortisol concentration studies revealed the following dependencies on the steroid: alpha-lactalbumin content was maximal between 0.01 and 0.1 microgram and, at 10 microgram/ml fell below the baseline level observed without cortisol. On the other hand, galactosyltransferase, lactose synthetase and lactose secretion were only slightly increased at 0.01 microgram/ml, were maximal between 0.1 and 1.0 microgram/ml, and at 10 microgram/ml were still considerably above the baseline levels observed without cortisol. These results indicate that lactose formation and secretion by mammary explants from virgin mice correspond more closely to the hormone-induced activity of galactosyltransferase than to that of alpha-lactalbumin, and that asynchrony can arise between the induction of alpha-lactalbumin and the induction of lactose.
D000818:Animals; D004790:Enzyme Induction; D005260:Female; D005700:Galactosyltransferases / Q000096:biosynthesis*; D006854:Hydrocortisone / Q000494:pharmacology; D007328:Insulin / Q000494:pharmacology; D007700:Kinetics; D007768:Lactalbumin / Q000096:biosynthesis*; D007785:Lactose / Q000378:metabolism*; D007788:Lactose Synthase / Q000096:biosynthesis*; D008321:Mammary Glands, Animal / Q000187:drug effects / Q000378:metabolism*; D009924:Organ Culture Techniques; D011388:Prolactin / Q000494:pharmacology; D051381:Rats; D014284:Triiodothyronine / Q000494:pharmacology
D007328:Insulin; D014284:Triiodothyronine; D011388:Prolactin; D007768:Lactalbumin; D005700:Galactosyltransferases; D007788:Lactose Synthase; D007785:Lactose; D006854:Hydrocortisone